Methoxsalen stimulates electrogenic Cl- secretion in the mouse jejunum

Genistein stimulates electrogenic Cl− secretion via phosphodiesterase modulation in the mouse jejunum

Previously, we demonstrated that genistein stimulated Cl− secretion in the mouse jejunum (Baker MJ and Hamilton KL, Am J Physiol Cell Physiol 287: C1636–C1645, 2004); however, the mode of action of genistein still remains unclear. Here, we examined the activation of Cl− secretion by the modulation of phosphodiesterases (PDEs) by genistein (75 μM) in the mouse jejunum with the Ussing short-circuit current ( Isc) technique. Drugs tested included theophylline (10 mM), a nonspecific PDE inhibitor; 8-methoxymethyl-3-isobutyl-1-methylxanthine (8-MM-IBMX; 100 μM), erythro-9-(2-hydroxyl-3-nonyl)-adenine (EHNA; 40 μM), milrinone (100 μM), and rolipram (40 and 100 μM), which are specific inhibitors of PDE1–PDE4, respectively. Theophylline stimulated a bumetanide-sensitive Isc, indicative of Cl− secretion, and abolished genistein's stimulatory action on Isc. Neither 8-MM-IBMX nor EHNA altered the basal Isc nor did these PDE inhibitors affect the stimulatory action of genistein on the Isc of the mouse jejunum. Rolipram had no effect on basal Isc, but it reduced the genistein-stimulated Isc compared with time-matched control tissues. Milrinone stimulated a concentration-dependent increase in Isc. Bumetanide (10 μM) inhibited 60 ± 4% of milrinone-induced Isc. Pretreating tissues with milrinone prevented genistein from stimulating Isc, and pretreatment with genistein reduced the effect of milrinone on Isc. H89 (50 μM), a PKA inhibitor, reduced the milrinone-stimulated Isc. Likewise, H89 reduced the genistein-stimulated Isc. Here, we demonstrate, for the first time, that genistein activates Cl− secretion of the mouse jejunum via inhibition of a PDE3-dependent pathway.

Long-term outcomes and prognostic factors in pediatric patients with severe traumatic brain injury and elevated intracranial pressure

OBJECT

The management strategies and outcomes in pediatric patients with elevated intracranial pressure (ICP) following severe traumatic brain injury (TBI) are examined in this study.

METHODS

This study was a retrospective review of a prospectively acquired pediatric trauma database. More than 750 pediatric patients with brain injury were seen over a 10-year period. Records were retrospectively reviewed to determine interventions for correcting ICP, and surviving patients were contacted prospectively to determine functional status and quality of life. Only patients with 2 years of follow-up were included in the study.

RESULTS

Ninety-six pediatric patients (age range 3-18 years) were identified with a Glasgow Coma Scale score<8 and elevated ICP>20 mm Hg on presentation. The mean injury severity score was 65 (range 30-100). All patients were treated using a standardized head injury protocol. The mean time course until peak ICP was 69 hours postinjury (range 2-196 hours). Intracranial pressure control was achieved in 82 patients (85%). Methods employed to achieve ICP control included maximal medical therapy (sedation, hyperosmolar therapy, and paralysis) in 34 patients (35%), ventriculostomy in 23 patients (24%), and surgery in 39 patients (41%). Fourteen patients (15%) had refractory ICP despite all interventions, and all of these patients died. Seventy-two patients (75%) were discharged from the hospital, whereas 24 (25%) died during hospitalization. Univariate and multivariate analysis revealed that the presence of vascular injury, refractory ICP, and cisternal effacement at presentation had the highest correlation with subsequent death (p<0.05). Mean follow-up was 53 months (range 11-126 months). Three patients died during the follow-up period (2 due to infections and 1 committed suicide). The mean 2-year Glasgow Outcome Scale score was 4 (median 4, range 1-5). The mean patient competency rating at follow-up was 4.13 out of 5 (median 4.5, range 1-4.8). Univariate analysis revealed that the extent of intracranial and systemic injuries had the highest correlation with long-term quality of life (p<0.05).

CONCLUSIONS

Controlling elevated ICP is an important factor in patient survival following severe pediatric TBI. The modality used for ICP control appears to be less important. Long-term follow-up is essential to determine neurocognitive sequelae associated with TBI.

DCEBIO stimulates Cl- secretion in the mouse jejunum

We investigated the effects of 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one(DCEBIO) on the Cl- secretory response of the mouse jejunum using the Ussing short-circuit current (Isc) technique. DCEBIO stimulated a concentration-dependent, sustained increase in Isc (EC50 41 +/- 1 microM). Pretreating tissues with 0.25 microM forskolin reduced the concentration-dependent increase in Isc by DCEBIO and increased the EC50 (53 +/- 5 microM). Bumetanide blocked (82 +/- 5%) the DCEBIO-stimulated Isc consistent with Cl- secretion. DCEBIO was a more potent stimulator of Cl- secretion than its parent molecule, 1-ethyl-2-benzimidazolinone. Glibenclamide or NPPB reduced the DCEBIO-stimulated Isc by >80% indicating the participation of CFTR in the DCEBIO-stimulated Isc response. Clotrimazole reduced DCEBIO-stimulated Isc by 67 +/- 15%, suggesting the participation of the intermediate conductance Ca2+-activated K+ channel (IKCa) in the DCEBIO-activated Isc response. In the presence of maximum forskolin (10 microM), the DCEBIO response was reduced and biphasic, reaching a peak response of the change in Isc of 43 +/- 5 microA/cm2 and then falling to a steady-state response of 17 +/- 10 microA/cm2 compared with DCEBIO control tissues (61 +/- 6 microA/cm2). The forskolin-stimulated Isc in the presence of DCEBIO was reduced compared with forskolin control tissues. Similar results were observed with DCEBIO and 8-BrcAMP where adenylate cyclase was bypassed. H89, a PKA inhibitor, reduced the DCEBIO-activated Isc, providing evidence that DCEBIO increased Cl- secretion via a cAMP/PKA-dependent manner. These data suggest that DCEBIO stimulates Cl- secretion of the mouse jejunum and that DCEBIO targets components of the Cl- secretory mechanism.

Genistein stimulates electrogenic Cl−secretion in mouse jejunum

We used the short-circuit current ( Isc) technique to investigate the effects of the isoflavone genistein on the electrogenic Cl−secretion of the mouse jejunum. Genistein stimulated a sustained increase in Iscthat was dose dependent. Bumetanide inhibited 76 ± 5% of the genistein-stimulated Iscconsistent with activation of Cl−secretion. Genistein failed to stimulate Iscfollowing maximal activation of the cAMP pathway by forskolin. In addition, forskolin had a reduced effect on Iscof the mouse jejunum in the presence of genistein. Glibenclamide, a blocker of CFTR, eliminated the genistein-stimulated increase of Iscand reduced the forskolin-activated Isc. Clotrimazole, a Ca2+-activated K+channel blocker, failed to reduce the genistein-stimulated Isc. Vanadate, a blocker of tyrosine-dependent phosphatases, reduced the genistein-activated Isc. Tyrphostin A23, a tyrosine kinase inhibitor, reduced basal Isc, after which genistein failed to stimulate Isc. These data suggest that genistein activated a sustained Cl−secretory response of the mouse jejunum and that the effect of genistein was via a tyrosine-dependent phosphorylation pathway.